Given the nation’s preoccupation with remembering that President Trump once promised to get Mexico to pay for a wall, some may have forgotten that he similarly pledged universal health coverage shortly before being inaugurated. As with Mexico’s payment, no universal coverage emerged during the two years that Republicans held unified control of Congress. Unlike the wall, Trump didn’t dig in his heels and force a government shutdown to get his way.

In fact, as Gallup reported Wednesday, the number of uninsured Americans has increased during Trump’s time in office, from a low at the end of Barack Obama’s second term in office — a function of the implementation of the Affordable Care Act (known more generally as Obamacare). The attitude of Trump’s administration toward Obamacare has varied from indifferent to overtly hostile.

The only significant change to the law that’s been made during Trump’s presidency is a repeal of the mandate that people have coverage. It is now the case that a fifth of those younger than 25 and more than a quarter of those who make less than $25,000 a year don’t.

Health care was a central issue in the 2018 midterms, with Democrats often focusing on the issue in campaign ads. Those ads leveraged Republican hostility to the Affordable Care Act and a lawsuit targeting the law to raise the specter of a decline in coverage and a loss of coverage for preexisting conditions — to good political effect for the party.

The more liberal arm of the Democratic Party, though, has been pushing for years to go further. What in 2004 was a fairly quiet push for single-payer — that is, government-centralized — health care championed by former Vermont governor Howard Dean had, by 2016, become Sen. Bernie Sanders’s (I-Vt.) Medicare-for-all campaign platform. As 2020 looms, announced Democratic primary candidates have broadly supported the idea of going a step further than Obamacare in ensuring coverage for all Americans.

This isn’t an uncommon pattern in presidential politics: In an effort to secure support from primary voters, who tend to be more politically extreme, candidates espouse positions that are further from center. The challenge, though, is that candidates might become committed to positions that become liabilities with the necessarily more-moderate electorate that votes in the general.

Polling from Kaiser Family Foundation released Wednesday suggests that Medicare-for-all could fall into that trap.

The pollsters offered four ways of changing the health-care system to expand coverage, including Medicare-for-all (which they described as “having a national health plan … in which all Americans would get their insurance from a single government plan”). A majority of Americans viewed the idea favorably to some extent — but it also had the most and strongest opposition.

Much of that was driven by strong opposition from Republicans. Slightly more than half of independents viewed the idea positively — but that’s much lower than the three-quarters who backed the other proposals included by KFF. Support among Democrats for Medicare-for-all wasn’t particularly strong, generally matching support for the other proposals.

What’s more, several arguments that might be used against the idea of creating a single-payer plan spurred sharp opposition to the proposal. That it guarantees coverage and would eliminate out-of-pocket costs was popular; that taxes might increase and delays might increase were not. (Note that some of these arguments would themselves be contested.)

Asked what they would like to see the House majority that swept into power in the 2018 midterms do, most Democrats picked bolstering Obamacare over passing Medicare-for-all.

That doesn’t necessarily mean they’d prefer a presidential candidate who prioritized Obamacare over Medicare-for-all; some respondents might be recognizing the reality that Trump, his rhetoric aside, almost certainly wouldn’t sign such a bill into law. As noted above, primary candidates are also in the business of pushing the envelope, often with hopes of at least improving existing legislation even if not achieving a more extreme policy goal.

In a normal year, in other words, embracing Medicare-for-all might seem like a risky proposition for a Democratic primary candidate. But 2020 will not be a normal year.

The Republicans are all but certain to nominate as their candidate the incumbent, Trump, who is deeply unpopular nationally and loathed by Democratic voters. Just as Trump benefited from antipathy by some toward Hillary Clinton in 2016, Trump’s eventual opponent will certainly benefit from Trump’s unpopularity. What’s more, Trump will probably again dominate much of the news coverage before the election — but this time, much will be focused on his administration, which is unlikely to appeal to many Democrats or independents.

This was the argument made by supporters of Sanders in 2016: That while his positions were more liberal than the norm (and than Clinton), he could have beaten Trump simply by virtue of not being Clinton running against a very unpopular Republican. The energy he engendered from Democratic primary voters might, they argue, have been key to goosing turnout enough for a victory.

Democratic primary candidates might well be justified in thinking that the primary is the harder of the two contests they’ll face in 2020. Therefore a run to the left — which energizes the base and secures the nomination — may be the best strategy.